Autocatalytic Decomplexation of Cu(II)-EDTA and Simultaneous Removal of Aqueous Cu(II) by UV/Chlorine.
Autocatalytic Decomplexation of Cu(II)-EDTA and Simultaneous Removal of Aqueous Cu(II) by UV/Chlorine.
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DOI：
10.1021/acs.est.8b05346
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发表时间：
2019-01
影响因子：
11.4
通讯作者：
Xianfeng Huang;Yi Wang;Xuchun Li;Dongxin Guan;Yubao Li;Xiangyong Zheng;Min Zhao;C. Shan;B. Pan
中科院分区：
文献类型：
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作者：
Xianfeng Huang;Yi Wang;Xuchun Li;Dongxin Guan;Yubao Li;Xiangyong Zheng;Min Zhao;C. Shan;B. Pan
传统工艺通常不能有效地从与有机配体络合的有毒重金属中去除水的污染。本文首次报道了紫外光/氯法去除铜(II)-EDTA的过程，其中铜(II)-EDTA的降解遵循自催化两阶段动力学，同时以CuO沉淀的形式去除铜(II)。清除实验和电子顺磁共振分析表明，在扩散控制速率下(∼1010M~(-1)S~(-1))，铜(II)-乙二胺四乙酸根的降解是由氯离子引起的。对11个关键中间体的机理研究表明，紫外光/氯降解铜(II)-EDTA是一个由铜(II)/铜(I)氧化还原循环介导的自催化连续脱羧基过程。在紫外光照射下，以配体-金属电荷转移(LMCT)方式光解氯离子攻击的络合铜(II)，生成铜(I)。自由和有机配体络合的铜(I)都能与ClO-形成二元/三元络合物，这些络合物通过金属-配体电荷转移(MLCT)被氧化回铜(II)，同时产生Cl·，从而对铜(II)-EDTA的去除起到自催化作用。考察了氯气投加量和pH值的影响，并以实际电镀废水和其他铜(II)有机络合物为例验证了该方法的技术可行性。本研究揭示了氯·解离的新机理，拓宽了UV/氯工艺在水处理中的应用前景。
Traditional processes usually cannot enable efficient water decontamination from toxic heavy metals complexed with organic ligands. Herein, we first reported the removal of Cu(II)-EDTA by a UV/chlorine process, where the Cu(II)-EDTA degradation obeyed autocatalytic two-stage kinetics, and Cu(II) was simultaneously removed as CuO precipitate. The scavenging experiments and EPR analysis indicated that Cl• accounted for the Cu(II)-EDTA degradation at diffusion-controlled rate (∼1010 M-1 s-1). Mechanism study with mass spectrometry evidence of 11 key intermediates revealed that the Cu(II)-EDTA degradation by UV/chlorine was an autocatalytic successive decarboxylation process mediated by the Cu(II)/Cu(I) redox cycle. Under UV irradiation, Cu(I) was generated during the photolysis of the Cl•-attacked complexed Cu(II) via ligand-to-metal charge transfer (LMCT). Both free and organic ligand-complexed Cu(I) could form binary/ternary complexes with ClO-, which were oxidized back to Cu(II) via metal-to-ligand charge transfer (MLCT) with simultaneous production of Cl•, resulting in the autocatalytic effect on Cu(II)-EDTA removal. Effects of chlorine dosage and pH were examined, and the technological practicability was validated with authentic electroplating wastewater and other Cu(II)-organic complexes. This study shed light on a new mechanism of decomplexation by Cl• and broadened the applicability of the promising UV/chlorine process in water treatment.